This invention generally relates to an improved container for explosive material. More particularly, the invention relates to an improvement in an explosive primer or booster of the general type including a sealed, cylindrical container for explosive material and a sleeve, encirclingly engaging the container, for holding detonators in close proximity to the container and its explosive contents. The purpose of the improvement is to hinder the sleeve from slipping off the container during normal usage.
Explosive primers or boosters to which this invention may apply are described by G. L. Griffith in U.S. Pat. No. 3,789,760 which issued Feb. 5, 1974, incorporated herein by reference. Such primers generally function well and possess significant advantages over other devices. It has been found that occasionally, however, the sleeve of such primers, which, heretofore, was held on only by friction, slips off the container during normal usage, thus allowing the detonators to fall away from the container. Because of the difference between the coefficients of thermal expansion of the container and its contents and the sleeve, this problem usually occurs when the primer is subjected to a sudden decrease in temperature, such as when it is placed in a borehole or other location where an explosive charge is being set. The container shrinks more rapidly than the sleeve, thus allowing the sleeve to slip off. The result of the detonators becoming detached from the container is usually a misfire. A misfire requires that a new primer be inserted into the explosive charge, and detonation attempted again, thus requiring the loss of time and materials and the creation of a potentially hazardous situation.
Accordingly, a need exists for a means for hindering the sleeve of such primers or boosters from slipping off the container, and allowing the detonators to become removed from the explosive material.